EFFECT OF NON-VOLATILE SOLUTES ON BOILING POINT AND VAPOR PRESSURE OF MIXED SOLVENT

The effects of some non-volatile solutes on the boiling point of alcohol (methanol,ethanol,1-propanol)/water binary mixed solvent were determined by isobaric VLE experiments,with mixed solvent composition held constant.The effects of sixteen various non-volatile solutes on the boiling point of 1-propanol/water azeotrope were included.A strict thermodynamic equation on the effect of non-volatile solute on VLE of binary mixed solvent was derived.By means of theoretical analysis of the equation,two conclusions of universal significance were obtained:(1) when a little non-volatile solute dissolves in a binary mixed solvent with constant composition,boiling point will be elevated or vapor pressure will be depressed with increasing vapor composition of the less volatile component;(2) when a little non-volatile solute dissolves in azeotrope,any kind of solute always causes elevation of boiling point or depression of vapor pressure no matter how the vapor composition changes.The above conclusions were verified with the experiments of this paper and relevant experimental data in the literature,all of the experiment results were in agreement with the above conclusions without exception.